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Search Results: 1 - 10 of 401471 matches for " M. Crisan "
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Temperature effect in the conductance of hydrogen molecule
M. Crisan,I. Grosu
Physics , 2008, DOI: 10.1016/j.physe.2008.06.027
Abstract: We present a many-body calculation for the conductance of a conducting bridge of a simple hydrogen molecule between $Pt$ electrodes.The experimental results showed that the conductance $G=dI/dV$ has the maximum value near the quantum unit $G_{0}=2e^{2}/h$. The $I-V$ dependence presents peak and dip and we consider that the electron-phonon interaction is responsible for this behavior. At T=0 there is a step in this dependence for the energy of phonons $\omega_{0}$ which satisfies $eV=\omega_{0}$. We calculated the conductance at finite temperature and showed that $dG(T)/dV\propto 1/4T\cosh^{2}\frac{eV-\omega_{0}}{2T}$.
Excitonic condensation in quasi-two-dimensional systems
M. Crisan,I. Tifrea
Physics , 2005, DOI: 10.1016/j.physleta.2005.07.091
Abstract: We present a low energy model for the Bose-Einstein condensation in a quasi-two-dimensional excitonic gas. Using the flow equations of the Renormalization group and a $\Phi^4$ model with the dynamical critical exponent $z=2$ we calculate the temperature dependence of the critical density, coherence length, magnetic susceptibility, and specific heat. The model can be relevant for the macroscopic coherence observed in GaAs/AlGaAs coupled quantum wells.
Ultrasonographic assessment of the cutaneous changes induced by topical flavonoid therapy
Crisan D, Crisan M, Moldovan M, Lupsor M, Badea R
Clinical, Cosmetic and Investigational Dermatology , 2012, DOI: http://dx.doi.org/10.2147/CCID.S25840
Abstract: rasonographic assessment of the cutaneous changes induced by topical flavonoid therapy Original Research (2313) Total Article Views Authors: Crisan D, Crisan M, Moldovan M, Lupsor M, Badea R Published Date January 2012 Volume 2012:5 Pages 7 - 13 DOI: http://dx.doi.org/10.2147/CCID.S25840 Received: 04 September 2011 Accepted: 17 October 2011 Published: 12 January 2012 Diana Crisan1, Maria Crisan2, Mirela Moldovan3, Monica Lupsor4, Radu Badea4 1Student, Faculty of Medicine, 2Department of Histology, 3Department of Dermopharmacy and Cosmetics, 4Department of Ultrasonography, University of Medicine and Pharmacy “Iuliu Hatieganu” Cluj-Napoca, Romania Abstract: Ultrasonography allows the quantification of dermal density and echogenicity changes during the physiological senescence process. Some active ingredients are able to slow down the tissular degeneration and disorganization process. The purpose of this study was to assess the cutaneous changes induced by the topical use of products containing Viniferol as active ingredient, using high-frequency ultrasound. The study was performed over 12 weeks and included 80 healthy Caucasian female subjects, aged 22–75 years, divided into two groups: the study group and the control group. The product was applied according to a predetermined protocol. The measurements performed for each subject were: the thickness of the epidermis and dermis (mm), the number of low, medium, and high echogenic pixels, and the number of low echogenic pixels in the upper dermis/number of low echogenic pixels in the lower dermis. All the parameters showed a significant improvement. Ultrasound measurements showed an increase of the mean thickness of the epidermis (P < 0.0001) and dermis (P < 0.0001) following the application of the Viniferol product as compared to the control group. The changes in the dermal echogenicity confirm the efficacy and direct action of Viniferol upon the cutaneous fibroblasts. No side effects related to the treatment were recorded. The study proves the efficacy of this active ingredient in the cutaneous senescence process as well, as the fact that anti-aging prophylaxis should be initiated in the 20–40 year critical age group. This interval involves specific changes in dermal echogenicity that quantify intense molecular, biochemical and structural changes, being thus mostly and highly responsive to the anti-aging therapy.
Ultrasonographic assessment of the cutaneous changes induced by topical flavonoid therapy
Crisan D,Crisan M,Moldovan M,Lupsor M
Clinical, Cosmetic and Investigational Dermatology , 2012,
Abstract: Diana Crisan1, Maria Crisan2, Mirela Moldovan3, Monica Lupsor4, Radu Badea41Student, Faculty of Medicine, 2Department of Histology, 3Department of Dermopharmacy and Cosmetics, 4Department of Ultrasonography, University of Medicine and Pharmacy “Iuliu Hatieganu” Cluj-Napoca, RomaniaAbstract: Ultrasonography allows the quantification of dermal density and echogenicity changes during the physiological senescence process. Some active ingredients are able to slow down the tissular degeneration and disorganization process. The purpose of this study was to assess the cutaneous changes induced by the topical use of products containing Viniferol as active ingredient, using high-frequency ultrasound. The study was performed over 12 weeks and included 80 healthy Caucasian female subjects, aged 22–75 years, divided into two groups: the study group and the control group. The product was applied according to a predetermined protocol. The measurements performed for each subject were: the thickness of the epidermis and dermis (mm), the number of low, medium, and high echogenic pixels, and the number of low echogenic pixels in the upper dermis/number of low echogenic pixels in the lower dermis. All the parameters showed a significant improvement. Ultrasound measurements showed an increase of the mean thickness of the epidermis (P < 0.0001) and dermis (P < 0.0001) following the application of the Viniferol product as compared to the control group. The changes in the dermal echogenicity confirm the efficacy and direct action of Viniferol upon the cutaneous fibroblasts. No side effects related to the treatment were recorded. The study proves the efficacy of this active ingredient in the cutaneous senescence process as well, as the fact that anti-aging prophylaxis should be initiated in the 20–40 year critical age group. This interval involves specific changes in dermal echogenicity that quantify intense molecular, biochemical and structural changes, being thus mostly and highly responsive to the anti-aging therapy.Keywords: ultrasonography, flavonoid therapy, cutaneous changes, anti-aging therapy
Transport and current noise characteristics of a T-shape double quantum dot system
K. Brown,M. Crisan,I. Tifrea
Physics , 2009, DOI: 10.1088/0953-8984/21/21/215604
Abstract: We consider the transport and the noise characteristics for the case of a T-shape double quantum dot system using the equation of motion method. Our theoretical results, obtained in an approximation equivalent to the Hartree-Fock approximation, account for non-zero on-site Coulomb interaction in both the detector and side dots. The existence of a non-zero Coulomb interaction implies an additional two resonances in the detector's dot density of states and thereafter affects the electronic transport properties of the system. The system's conductance presents two Fano dips as function of the energy of the localized electronic level in the side dot. The Fano dips in the system's conductance can be observed both for strong (fast detector) and weak coupling (slow detector) between the detector dot and the external electrodes. Due to stronger electronic correlations the noise characteristics in the case of a slow detector are much higher. This setup may be of interest for the practical realization of qubit states in quantum dots systems.
Non-Fermi behavior of the disorder electronic system
C. P. Moca,I. Tifrea,M. Crisan
Physics , 1999,
Abstract: We showed that an electronic system with weak disorder considered in the finite-charge infinite U Hubbard model can present a non-Fermi behavior. The imaginary pert of the self-energy has been calculated and a linear temperature dependence was obtained. This result is in agreement with the non-Fermi behavior observed at the insulator-metal crossover in La_{2-x}Sr_xCuO_4.
Field-Theoretical description of the crossover between BCS and BEC in a non-Fermi superconductor
C. P. Moca,I. Tifrea,M. Crisan
Physics , 1999,
Abstract: Using the field-theoretical methods we studied the evolution from BCS description of a non-Fermi superconductor to that of Bose-Einstein condensation (BEC) in one loop approximation. We showed that the repulsive interaction between composite bosons is determined by the exponent $\alpha$ of the Anderson propagator in a two dimensional model. For $\a\neq 0$ the crossover is also continous and for $\a=0$ we obtain the case of the Fermi liquid.
Zero temperature conductance of parallel T-shape double quantum dots
M. Crisan,I. Grosu,I. Tifrea
Physics , 2007, DOI: 10.1016/j.physe.2007.04.008
Abstract: We analyze the zero temperature conductance of a parallel T-shaped double quantum dot system. We present an analytical expression for the conductance of the system in terms of the total number of electrons in both quantum dots. Our results confirm that the system's conductance is strongly influenced by the dot which is not directly connected to the leads. We discuss our results in connection with similar results reported in the literature.
Fluctuation contribution to the specific heat in non-Fermi models for superconductivity
I. Tifrea,I. Grosu,M. Crisan
Physics , 1998,
Abstract: We investigate the fluctuation contribution to the specific heat of a two-dimensional superconductor with a non-Fermi normal state described by a Anderson Green's function $G(k,i\omega)=\omega_c^{-\alpha}/(i\omega-\epsilon_k)^{1-\alpha}$. The specific heat corrections contain a term proportional to $(T^{2\alpha-T_c^{2\alpha}})^{-1}$ and another logarithmic one. We defined a coherence length as function of the non-Fermi parameter $\alpha$, which showed that a crossover study between BCS and Bose-Einstein condensation is possible by varying $\alpha$ in an interval $0 \div \alpha_{cr}$. By comparing our theoretical results with the experimental data for HTSC materials, we reobtained the value for $\alpha$, corresponding to such systems, of the order $0.3 \div 0.45$. We also reobtained the critical temperature for such a superconductor using the Thouless criterion.
Metallic Glass in Two Dimensional Disordered Bose System; A Renormalization Group Approach
M. Crisan,I. Grosu,I. Tifrea
Physics , 2008,
Abstract: We consider the two dimensional disordered Bose gas which present a metallic state at low temperatures. A simple model of an interacting Bose system in a random field is propose to consider the interaction effect on the transition in the metallic state.
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